Radical scavenging activity of dicaffeoyloxycyclohexanes: Contribution of an intramolecular interaction of two caffeoyl residues
Radical scavenging activity of dicaffeoyloxycyclohexanes: Contribution of an intramolecular interaction of two caffeoyl residues
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DOI：
10.1016/j.bmc.2005.04.049
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发表时间：
2005-07-01
影响因子：
3.5
通讯作者：
Kawabata, J
中科院分区：
文献类型：
--
作者：
Saito, S;Kurakane, S;Kawabata, J
以二咖啡酰奎尼酸为模型化合物，合成了6种二咖啡酰氧基环己烷和2，4-二-O-咖啡酰-1，6-脱水-β-D-葡萄糖的区域和立体异构体，并通过DPPH（2，2-二苯基-1-苦肼基）和ABTS（2，2 '-偶氮双（3-乙基苯并噻唑啉-6-磺酸）二铵盐）自由基清除试验评价了它们的自由基清除活性。这些化合物清除DPPH和ABTS自由基的反应均由两个不同的步骤组成。在第一步中，咖啡酰残基的儿茶酚部分迅速转化为邻醌结构，并且在测试化合物之间观察到反应性没有显著差异。然而，在第二步中，反应的速率随着两个咖啡酰残基的分子内距离的减小而增加。从反式-1，2-二咖啡酰氧基环己烷与DPPH自由基的反应混合物中分离出一种新的分子内偶联产物，该产物能与其它自由基发生偶联反应。结果表明，自由基清除反应的第二步是由两个咖啡醌残基之间的分子内相互作用产生的，以再生邻苯二酚结构，并且它们的距离越近，它们的反应越快。天然二咖啡酰奎尼酸在生物水体系中的自由基清除活性也可能取决于咖啡酰酯基团的位置。(c)2005爱思唯尔有限公司保留所有权利。
Six regio- and stereoisomers of dicaffeoyloxycyclohexanes and 2,4-di-O-caffeoyl-1,6-anhydro-beta-D-glucose were synthesized as model compounds of dicaffeoylquinic acids, and their radical scavenging activity was evaluated by DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt) radical scavenging tests. Both DPPH and ABTS radical scavenging reactions of these compounds consisted of two different steps. In the first step, catechol moieties of the caffeoyl residues were rapidly converted to o-quinone structures and no significant difference in the reactivity was observed among the tested compounds. In the second step, however, the rate of the reaction increased as the intramolecular distance of the two caffeoyl residues decreased. A novel intramolecular coupling product, which could scavenge additional radicals, was isolated from the reaction mixture of trans-1,2-dicaffeoyloxycyclohexane and DPPH radical. The result suggests that the second step of the radical scavenging reaction is arising from an intramolecular interaction between the two caffeoquinone residues to regenerate catechol structures, and that the closer their distance is, the more rapidly they react. The radical scavenging activity of natural dicaffeoylquinic acids in a biological aqueous system might also depend on the positions of caffeoyl ester groups. (c) 2005 Elsevier Ltd. All rights reserved.